﻿// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

#nullable disable

using System.Runtime.Versioning;
using System.ServiceProcess;

namespace Microsoft.DotNet.Cli.Installer.Windows;

/// <summary>
/// Provides a simple abstraction of the Windows Update service.
/// </summary>
[SupportedOSPlatform("windows")]
internal sealed class WindowsUpdateAgent
{
    private readonly ServiceController _wuauserv;

    private readonly ISetupLogger _log;

    private bool _wasRunning;
    private bool _wasStopped;

    /// <summary>
    /// Creates a new <see cref="WindowsUpdateAgent"/> instance.
    /// </summary>
    /// <param name="logger">The <see cref="ISetupLogger"/> to write to.</param>
    public WindowsUpdateAgent(ISetupLogger logger)
    {
        _wuauserv = ServiceController.GetServices().Where(s => string.Equals(s.ServiceName, "wuauserv")).FirstOrDefault();
        _log = logger;

        if (_wuauserv == null)
        {
            _log?.LogMessage("Unable to locate wuaserv.");
        }
    }

    /// <summary>
    /// Stops the Windows Update service (wuauserv) if it is currently running and stoppable, otherwise
    /// logs the status of the service.
    /// </summary>
    public void Stop()
    {
        if (_wuauserv == null)
        {
            return;
        }

        if (_wuauserv.Status == ServiceControllerStatus.Running && _wuauserv.CanStop)
        {
            try
            {
                // Remember that the service was running so when we exit, we can restart it.
                _wasRunning = true;
                _log?.LogMessage("Stopping automatic updates.");

                // Ideally we want to pause and resume the service using WUAPI, but that is no longer
                // supported on Windows 10. See https://docs.microsoft.com/en-us/windows/win32/api/wuapi/nf-wuapi-iautomaticupdates-pause)
                _wuauserv.Stop();
                _wuauserv.WaitForStatus(ServiceControllerStatus.Stopped, new TimeSpan(0, 0, 30));
                _wasStopped = true;
            }
            catch (Exception e)
            {
                _log?.LogMessage($"Failed to stop automatic updates: {e.Message}");
            }
        }
        else
        {
            _log?.LogMessage($"wuauserv, status: {_wuauserv.Status}, can stop: {_wuauserv.CanStop}");
        }
    }

    /// <summary>
    /// Starts the Windows Update service (wuauserv) if it was previously stopped by calling <see cref="Stop"/>
    /// and it is currently stopped.
    /// </summary>
    public void Start()
    {
        if (_wuauserv == null)
        {
            return;
        }

        // Only start the service if it was running, we stopped it and it is currently stopped.
        if (_wuauserv.Status == ServiceControllerStatus.Stopped && _wasRunning && _wasStopped)
        {
            try
            {
                _log?.LogMessage("Starting automatic updates.");
                _wuauserv.Start();
                _wuauserv.WaitForStatus(ServiceControllerStatus.Running, new TimeSpan(0, 0, 30));
            }
            catch (Exception e)
            {
                _log?.LogMessage($"Failed to start automatic updates: {e.Message}");
            }
        }
        else
        {
            _log?.LogMessage($"wuauserv, status: {_wuauserv.Status}, was running: {_wasRunning}, was stopped: {_wasStopped}");
        }
    }
}
